Spinal Cord B&B

Question 1

the vertebral disc is called the _____ and is a remnant of the embryological _____

Answer 1

the vertebral disc is called the nucleus pulposus and is a remnant of the embryological notochord

Question 2

where is the grey and white matter found, respectively, in the spinal cord cross-section, and what is contained in each?

Answer 2

white matter = outer = nerve fibers

grey matter = inner = cell bodies

Question 3

how can you tell from a spinal cross-section if you are in the thoracic region?

Answer 3

thoracic spinal cord has little bumps on the sides of the grey (inner) matter containing sympathetic cell bodies called the lateral horns

Question 4

what types of cell bodies are found in the posterior/dorsal, anterior/ventral, and lateral horns of the spinal cord?

Answer 4

posterior = sensory (spinothalamic tract and dorsal column)

lateral = sympathetic (thoracic spinal cord only)

anterior = motor (lateral corticospinal tract)

Question 5

all sensory information except for ____ relays through the thalamus

Answer 5

all except for smell

Question 6

what kind of information does the spinothalamic tract carry? how many neurons are involved in this pathway, and where do they synapse?

Answer 6

spinothalamic = pain/temperature/crude touch

3 neuron system:
1. spinal root to cord
2. dorsal horn to thalamus (crosses over at dorsal horn level)
3. VPL (ventral posterolateral nucleus) thalamus to cortex

Question 7

what kind of information does the posterior column (dorsal column-medial lemniscus) carry? how many neurons are involved in this pathway, and where do they synapse?

Answer 7

sensory (afferent) pathway, carrie’s information from Meissner’s (touch) and Pacinian (vibration/pressure) corpuscles

3 neuron system:
1. into spinal root, traveling up posterior cord
2. synapse at Gracilis (thorax, legs) or Cuneatus (arms) nuclei in lower medulla, which cross over (decussation) and ascend
3. VPL (ventral posterolateral nucleus) thalamus to cortex

Question 8

from where does the Gracilis vs Cuneatus nuclei of the lower medulla receive sensory information?

Answer 8

Gracilis (upper) = thorax + legs
Cuneatus (lower) = arms

receives afferent info from neurons traveling in posterior column of spinal cord - after reaching lower medulla, 2nd neuron crosses over (decussation) before synapsing at VPL thalamus

Question 9

where does decussation occur in the spinothalamic tract vs posterior column? why is this clinically relevant?

Answer 9

spinothalamic (pain/temp/crude touch): cross over at level of dorsal horn

posterior column (vibration/proprioception/fine touch): cross over in lower medulla (after synapsing at Gracilis or Cuneatus nuclei)

lesion before decussation = ipsilateral symptoms, lesion after decussation = contralateral symptoms

Question 10

how many neurons are involved in the corticospinal tract, and where do these synapse? where does decussation occur?

Answer 10

corticospinal tract = motor/efferent information

2 neurons:
1. cortex to anterior horn
2. anterior horn to muscle

decussation at lower medulla

Question 11

what is the Romberg test used for?

Answer 11

Romberg test: patient closes their eyes, assess if they can remain balanced

testing function of posterior column of spinal cord (touch/proprioception/vibration)